Modern tungsten incandescent lamps are developed at the turn of the twentieth century. The light emitting body therein is a tungsten filament. This material features a high melting point, which maintains its solid state in high temperatures. Thereby, the bulbs can have longer lifetime; the filaments will not burn down in a short time. Practically, a temperature of the filament of a lighted incandescent bulb is as high as 3000° C.; it is the light radiation produced by the incandescent filament to make the bulb emit bright rays of light. Thereafter, nights no longer hold back people's lives. With the light brought by incandescent bulbs, night activities, no matter in work or living, can go on with great convenience and enabling many possibilities. The invention of incandescent bulbs significantly changes people's lifestyle; the time slots for activities are extended in many aspects, and thus facilitating developments of various kinds.
With the progress of lighting technologies, various lighting bulbs are developed. Among all electrical lighting bulbs, incandescent bulbs are the least efficient. They have a very bad energy conversion rate of only 12˜18%; the rest energy is dissipated and wasted in the thermal form. Thanks to the advancement and maturity of the LED, peripheral integrate-circuit control device, and heat dissipating technologies, the applications of LEDs are diversified from low-power power indicators and light sources for mobile phones to LED backlight modules and general lighting products. Thereby, LEDs are replacing traditional light sources gradually. In comparison with the short lifetime and heat of incandescent bulbs, LEDs have the advantages of low power consumption, no mercury, no halides, and low carbon-dioxide emission. Considering the environmental protection issues, many countries have set a time limit to prohibit incandescent bulbs for saving energy, reducing carbon, and reducing usage of mercury and halides, and turn to promote LEDs completely.
Besides, because LEDs are point light sources, they have more design flexibility. A bulb can be made with distributed light sources and hence not offending to the eye. Alternatively, the light of a bulb can be made to concentrate at a point or over a specific region. The produced colors can be more vivid and bright. Presently, the light emitting efficiency of a white-light LED has reached 70 lm/W, which exceeds 15 lm/W of an incandescent bulb. Nonetheless, currently, only 35% of the input power to an LED is converted to light with the rest 65% s converted to heat, which is the main cause deteriorating the light emitting efficiency of the LED. In addition, if the heat dissipating mechanism of the overall device is not good, the generated heat by the LED will accumulate therein and cannot be dissipated immediately, which will shorten the lifetime of the LED. Generally, the lifetime of an LED bulb is above 100,000 hours. However, if the operating temperature is greater than 85° C., its lifetime will be greatly reduced.
Accordingly, while bulbs, including LED bulbs, are being used, increase in heat is an inevitable result. Heat dissipation is the scheme for solving this problem. The focus of related technologies will be put on how to enhance the heat dissipating efficiency of various parts for accelerating heat dissipation and thus improving the lifetime. In an LED bulb, there are two heat sources, including the light sources and the power driver. The heat dissipation for both should be performed. If the heat dissipating mechanism is not good, the heat generated by the light sources will be transferred to the central part through heat conduction. Then the co-heating effect between the heat generated by the light sources and the heat generated by the power driver will occur. Owing to the effect, the internal temperature will be excessively high, damaging the electronic components in the power driver. In addition to affecting the lifetime of the power driver severely, the light emitting efficiency will be reduced because the co-heating effect keeps the temperature of the light sources high. This is usually caused by damages inside the power driver but not by the problem in the light emitting efficiency of the light sources. Moreover, in addition to reducing the lifetime of the bulb, the co-heating-effect-induced temperature rise also raises the room temperature and hence making users uncomfortable. Thereby, heat dissipating mechanism is a very important subject is this field.
While various bulbs are being used, if the heat dissipating mechanism is not designed in the lamp stand, the heat generated by the light sources and the power driver is hard to be removed and producing bad influences. Accordingly, the present invention provides an LED bulb, which is mainly applied to the heat dissipation of the bulb. The lamp cup of the LED bulb according to the present invention is a hollow two-piece structure. It is divided into a lamp-cup part and a light receiving part. After assembling with the power connecting part, an integral and smooth appearance is formed. The heat generated by the substrate placed in the lamp-cup part and by the power driver in the power connecting part of the lamp cup is dissipated through the lamp cup or outwards directly. Thereby, the co-heating effect induced by the substrate and the power driver can be solved effectively. For better heat dissipating effect, the bulb can be manufactured using materials with superior heat dissipating capability; for even better effect, the corresponding heat dissipating members can be used, too. Besides, it should be assembled by wedging for easier and more convenient fabrication. Accordingly, in addition to improving the lifetime of the bulb, the structure is safer more users; various problems caused by high temperature can be avoided.